Whey or natural proteins: which one builds the most muscle?

A tub of whey costs the price of several kilos of chicken. The promise: a "superior" protein, absorbed faster, that would build more muscle than a real meal. Research proves whey right on one specific point — and wrong on almost everything else. Here is what studies comparing powder to the plate, head-to-head, actually say.

First, what a protein powder actually provides

Let's start with the most solid figure in the field. A 2018 meta-analysis pooled protein supplementation trials in healthy adults engaged in resistance training. It finds a real and significant effect: +2.49 kg on strength (1RM) and +0.30 kg of fat-free mass.

Three hundred grams of muscle. It is true, it is measured, and it is very far from what the packaging suggests. Two clarifications from the same work: the effect decreases with age, and it is more pronounced in already trained people — those who make progress least easily are the ones whom supplementation helps the most.

A 2010 review summarizes the position in favor of whey: among dairy proteins, it is the one that is said to cause the greatest increase in synthesis and, during training, the largest muscle cross-sectional area. This is the thesis that the rest of this article will pit against the trials.

The point where whey actually wins: speed

The advantage of whey is not a marketing invention. A 2009 study gave young men the same amount of essential amino acids in three forms — hydrolyzed whey, casein, or soy isolate — and measured muscle protein synthesis. Whey clearly wins:

Whey is digested quickly, it is rich in leucine, and it triggers a higher muscle protein synthesis peak than the others. This point is established. The whole question is whether this peak, measured over a few hours, turns into muscle after several months.

Where whole food catches up — and sometimes surpasses

As soon as powder is compared to real food, the gap closes. And in at least one case, it reverses.

Furthermore, the egg goes beyond just a training session: in overweight older adults, a diet with 1.4 g of protein per kilo including three whole eggs per day preserved lean mass whereas a diet at 0.8 g/kg without eggs did not. And a trial is underway to compare, in the long term, 30 g of beef steak protein to 30 g of whey — its results are not yet published.

The study that puts everyone on the same page

In 2017, a team made untrained young men work for 12 weeks divided into five groups: whey concentrate, hydrolysed whey, soy concentrate, leucine alone… and placebo.

All groups gained the same thing: +2.2 kg of muscle mass, with comparable increases in type I and type II fiber surface area. Including the placebo. The reason is given by the authors: everyone had increased their calories and was already consuming 1.1 to 1.3 g of protein per kilo and per day. When the dietary base is correct, powder adds nothing at all.

But not all studies agree

It would be dishonest to stop there. The trial most favorable to whey is also the longest: 9 months of daily supplementation in untrained men and women, whey vs soy vs carbohydrates.

A point for whey, then — but look at the intervals shown on the bars: they overlap largely, which means that from one participant to another the results cross. And note the detail that matters: the soy group, despite the same protein intake of 1.4 g/kg/day, gains less lean mass than the carbohydrate group. A result that is difficult to explain solely by protein quality, and which calls for caution before drawing a general rule from a single trial.

And plant proteins?

This is the only place where the source truly deserves your attention. A 2018 review explains why: plant proteins have on average a lower digestibility, less leucine and fewer essential amino acids. Equal amounts of them are less effective.

But "less effective in equal amounts" is not "ineffective". The 2021 meta-analysis that compared animal and plant proteins in randomized trials finds no difference in absolute lean mass or strength. The only animal advantage appears on the percentage of lean mass in under-50s (0.41 kg). And above all, the solution is known: increase the dose or combine sources. A 2021 study verified this — 40 g of protein from a plant blend enriched with lysine stimulated muscle synthesis as much as 40 g of chicken (0.046 %/h vs 0.055 %/h, non-significant difference).

Nuance to know: a 2018 pilot study observed lower muscle mass in vegan men than in vegetarians and omnivores, and a 2022 perspective warns of the risk of insufficient protein intake in elderly vegans. These works do not compare proteins at equal intake — they describe real diets, where the protein total is often lower. It is indeed the total that must be monitored.

Modern substitutes actually fare better than raw legumes. With 40 g of protein from a lysine-enriched plant meat substitute, young men's muscle synthesis rose from 0.031 to 0.046 %/h — compared to 0.055 %/h with chicken. Less, then, but not from another world.

How much protein per day, then?

Since the total takes precedence over the source, you might as well know the thresholds. A 2022 meta-analysis established them according to age:

For 75 kg, that comes to around 120 g per day. It is achievable with eggs, chicken, fish, dairy products, legumes — or with a shake on days when the meal does not fit into the day.

In summary

Whey is therefore not a magical product, but it is not a scam either: it is a convenient solution, practical and inexpensive per gram of protein, to bridge the gap between what you eat and what you should eat. If this gap is zero, you can keep your money.

And if you are wondering which supplements truly deserve your money, we have ranked the best-proven ones in bulking: the best-proven supplements.

Every figure in this article comes from a study that you can open: the underlined mentions lead to the work from which the result is drawn. These summaries are written solely from the abstract. Several of these trials involve untrained or elderly people, over durations of 8 weeks to 9 months, and the results do not all agree — this is pointed out in the text. Informational content, which does not replace professional advice.